Points comprising a reinforced switch tongue blade

ABSTRACT

In a switch including a main track and a branch track, wherein one rail of each track is each configured as a tongue rail and movable into abutment on the respective stock rail, at least one stock rail ( 1 ), in its region of abutment on the tongue rail ( 2 ), is designed to have a reduced rail head width as compared to the region located outside said region of abutment, wherein the rail head width, starting from the tip ( 3 ) of the tongue, decreases as far as to a point ( 4 ) at which the carrying wheel comes into lateral contact with the tongue rail ( 2 ) and increases in the region following thereupon, and that the tongue rail ( 2 ) is designed to be reinforced in cross section towards the stock rail ( 1 ) according to the reduction in the width of the stock rail head.

The invention relates to a switch including a main track and a branchtrack, wherein one rail of each track is each configured as a tonguerail and movable into abutment on the respective stock rail.

When passing a switch, high forces and, in particular, high transverseforces depending, in particular, on the radius of curvature and thedeviation angle of the switch, on the speed at which the switch ispassed, and on the axle load, are exerted on the rails. The majorportion of these transverse forces must be taken up by the tongue rail,wherein especially high loads caused by the high inertial andcentrifugal forces are to be observed, in particular, with inside curveswitches, in which the branch track branches off a curved main tracktowards the inner side of the curve. This entails increased wear and aconsiderably reduced life time. Moreover, modern switches have to bepassable at very high speeds, which will inevitably lead to tongue railshaving long, thin tips and hence elevated susceptibility to wear.Consequently, it has already been proposed several times to producetongue rails of special, wear-resistant materials or harden them bysubsequent treatment. This involves, however, a number of disadvantages,wherein, for instance, head-hardened tongue rails will generally not beemployed for safety reasons, because possible wear phenomena on thetongue rail should be visible so as to enable the premature recognitionof possible risks of fracture. Yet, fractures with head-hardened tonguerails are mostly brittle fractures, which make early detectionimpossible.

In the past, thickness-reinforced tongue rails have, therefore, beenfrequently proposed to enable the safe absorption of transverse forces.Thus, tongue rails have become known from German Offenlegungsschrift No.2,046,391, whose tongue ends comprise reinforcements in the directiontowards the stock rails, to which recesses provided on the inside edgesof the stock rails correspond. The tongue rail, in its position adjacentthe stock rail, engages in the recesses of the stock rail so as toprovide a continuous running edge in the region of transition from thestock rail to the tongue. However, in the configuration according toGerman Offenlegungsschrift No. 2,046,391, the recesses provided in thestock rail cause substantial weakening of the stock rail, and it is,therefore, necessary to fill the recesses of the stock rail withtightening keys in the open position of the tongue. From EP 040 533 A2it is, furthermore, known to reduce the width of a stock rail in itshead and foot regions in a zone in which the tongue rail abuts on thestock rail, so as to enable the tongue to be designed in correspondencewith the profile of the rail head in this transition region. Yet, withthat solution too, the profile of the stock rail is strongly weakened,thus causing an elevated risk of fracture. In order not to have toextensively reduce the cross section of the stock rail while,nevertheless, obtaining an adequate reinforcement of the tongue rail,the rail head profile of the stock rail is frequently milled offobliquely downwards in the region of contact of the tongue, as is, forinstance, disclosed in German Patent No. 487 877.

In the main, the proposals that have become known for reinforcing thecross section of a tongue rail in the region of abutment are not to beregarded as fully satisfactory, since no substantial improvement of thewear resistance of tongue rails has been observed and, in addition,undesired changes in the course of the inside edge are brought about bythe material reduction on the inside edge of the stock rail. Deviationsfrom the straight-line course of the inside edge produce harsh shocks onthe vehicle at high speeds and will, therefore, have to be avoided inany event. The object of the present invention is consequently toprovide a tongue rail that offers an enhanced wear resistance andextended working life by a reinforcement of the tongue in its frontregion so as to increase safety by avoiding any risk of fracture, whilethe original course of the inside edge, at the same time, is to beaffected as little as possible in order to increase comfort when passingthe switch.

To solve this object, the invention essentially consists in that atleast one stock rail, in its region of abutment on the tongue rail, isdesigned to have a reduced rail head width as compared to the regionlocated outside said region of abutment, wherein the rail head width,starting from the tip of the tongue, decreases as far as to a point atwhich the carrying wheel comes into lateral contact with the tongue railand increases in the region following thereupon, and that the tonguerail is designed to be reinforced in cross section towards the stockrail according to the reduction in the width of the stock rail head. Bymaking the reduction in the width of the stock rail cross section, orreinforcement of the tongue rail, not uniformly strong in the region ofabutment of the tongue rail on the stock rail, but allow it to increasein a first region and decrease in a second region following thereupon,it has become feasible to adapt the degree of reinforcement of thetongue rail to the course of the transverse forces.

When passing a switch, particularly high forces will act on the tonguerail in the region in which the carrying wheel comes into lateralcontact with the tongue rail, and that is why according to the inventionthe width of the rail head is designed to decrease from the tip of thetongue as far as to a point at which the carrying wheel comes intolateral contact with the tongue rail, and to increase in the regionfollowing thereupon until the end of abutment of the tongue rail on thestock rail, whereby the tongue rail is naturally designed to bereinforced according to this course. The largest reinforcement of thetongue rail is, thus, provided in the sensitive transition region of theload from the stock rail to the tongue rail, and, as a result, anincrease in the cross section and hence an increase in the moment ofinertia of the tongue rail are obtained, which enable the tongue rail tobetter withstand the elevated transverse forces. At the same time, thecourse of the inside edge of the stock rail changes only negligibly suchthat no adverse effects in the running behaviour are to be observed withthe open tongue. Due to the preferably constant cross-sectional change,jerky track changes will be avoided such that the ride comfort will notbe negatively influenced and shock loads on the rails will be inhibited.

The inside or running edge of a rail on the rail head is present on thewidest site as measured at a predefined or standardized verticaldistance from the top edge. In this case, the width of the stock railhead, which according to the invention is preferably designed toinitially decrease in the region of abutment of the tongue rail andsubsequently increase, is measured at a vertical distance of 10 to 20mm, particularly 14 mm, from the top edge. In order to weaken as littleas possible the cross section of the stock rail while, nevertheless,reaching sufficient reinforcement of the tongue rail, the configurationadvantageously is further developed such that the stock rail is designedto be chamfered in the region of abutment of the tongue rail with thechamfer extending in an inclined manner from the inside edge towards therail web. Such a chamfer departing from the inside edge of the stockrail, in addition, renders feasible to design the tongue in a reinforcedmanner without excessively affecting the course of the inside edge.

In the rounded region on the transition between the top edge and theinside edge, the intersection of the chamfer with the profile of thestock rail head naturally results in an edge that is contacted by thewheel flange of the carrying wheel. According to a preferred embodimentof the switch according to the invention, said edge resulting from theintersection of the chamfer with the profile of the stock rail head isdesigned to be rounded, said rounded design being, moreover,advantageously devised in a manner that the profile of the stock railhead is designed with a curvature on the transition from the top edge tothe chamfer, the radius of which curvature is smaller than that of thecorresponding curved region of the profile of a standard rail. Anoverhang is, thus, formed in this region such that only a very slighttrack change will occur despite the reduction in the width of the stockrail head. In addition, such a configuration helps optimize the contactgeometry between the flange of the carrying wheel in the transitionregion of the carrying wheel from the stock rail to the tongue rail suchthat a particularly jerk-free transition will be ensured in this region.

A particularly stressable and wearable switch will result, if thelargest reinforcement of the tongue rail is provided in that region inwhich the carrying wheel comes laterally into contact with the tonguerail as already mentioned, and, according to a preferred configuration,the switch according to the invention is, therefore, further developedin a manner that the point with the largest reinforcement of the tonguerail, or smallest width of the stock rail head, is located at a distancefrom the tip of the tongue, which amounts to ⅕ to ⅓, preferably ¼, ofthe length of the region of abutment of the tongue rail on the stockrail. The largest deviation of the course of the inside edge from thestandard course naturally is to be observed on that point, and theextent of reinforcement of the tongue rail, or reduction in the width ofthe stock rail, therefore is to be chosen such that an enhanced wearresistance at a simultaneous change in the inside edge as small aspossible will be ensured. In this context, a particularly advantageousconfiguration will be achieved if the maximum width reduction of thestock rail, or maximum reinforcement of the tongue rail, is 2 to 5 mmand, preferably, 3 mm.

As already mentioned, a particularly jerk-free transition of thecarrying wheel from the stock rail to the tongue rail is sought, and inthis context the switch according to the invention in an advantageousmanner is further developed such that the vertical height of the tonguerail increases in the region of abutment on the stock rail in thedirection towards the end of abutment, departing from the tip of thetongue. This ensures a continuous transition of the rolling load fromthe stock rail onto the tongue rail, whereby the contact geometry willbe further improved in this region, if, as in accordance with apreferred configuration, the inner flank of the flange of the carryingwheel, which preferably encloses an angle of 50° to 70° and, inparticular, 60° with the axle of the carrying wheel, extends parallelwith a tangent drawn at the tongue rail and the stock rail, or contactsthe rails along that tangent, at least in the region of the largestreinforcement of the tongue rail. This ensures the contact of thecarrying wheel with both the tongue rail and the stock rail,particularly in the region of overriding of the tongue rail by thecarrying wheel, despite the reinforcement of the tongue cross section,whereby the carrying wheel is prevented from ascending.

As already mentioned, the reinforcement according to the invention ofthe cross section of the tongue rail, and the enhanced wear resistanceresulting therefrom, are of particular advantage in switch geometries inwhich high transverse forces occur. The switch according to theinvention is, therefore, advantageously comprised of an inside curveswitch, wherein the curve outer tongue rail is designed to be reinforcedin cross section. The fact that, in the event of inside curve switches,particularly high transverse forces act on the curve outer tongue railbecause of the smaller radius of curvature and the enlarged deviationangle is thereby taken into account.

In the following, the invention will be explained in more detail by wayof an exemplary embodiment schematically illustrated in the drawing.Therein:

FIG. 1 is a top view on the switch region in which the tongue rail comesinto abutment on the stock rail;

FIG. 2 is a section along line 2-2 of FIG. 1;

FIG. 3 is a section along line 3-3 of FIG. 1;

FIG. 4 is a section along line 4-4 of FIG. 1,

FIG. 5 is an enlarged illustration of the stock rail head according toFIG. 3; and

FIG. 6 is an enlarged sectional illustration of the stock rail head withthe abutting tongue rail according to FIG. 3.

In FIG. 1, the stock rail of the main track is denoted by 1 and thetongue rail of the branch track is denoted by 2, only that region inwhich the tongue rail 2 contacts the stock rail 1 being illustrated. Therunning or inside edge is formed on the respectively widest site of thestock rail 1, wherein it is apparent from FIG. 1 that the inside edgedoes not extend linearly, but that the width of the stock rail 1 isdesigned to decrease from the region of the tip 3 of the tongue of thetongue rail 2 as far as to region 4 and increase again in the regionfollowing thereupon, from which results a buckled course of the insideedge 5. The tongue rail 2 is reinforced in the direction towards thestock rail 1 according to the reduction in width of the stock rail 1,the largest reinforcement being provided in the region 4 in which thecarrying wheel comes into lateral contact with the tongue rail. From thesectional views according to FIGS. 2, 3 and 4, it is only apparent thatthe reduction in width of the stock rail head is obtained by a chamferor undercut on the rail head. The extent of the undercut is the largestin the region 4 to which the sectional view according to FIG. 3corresponds and in which the tongue rail 2 is, thus, most stronglywidened, since the wear due to jerkily introduced transverse forces isthe largest in this region. From the sectional views according to FIGS.2, 3 and 4, it is further apparent that the vertical height of thetongue rail 2 is designed to increase from the tip 3 of the tongue asfar as to a region near the end of the abutment of the tongue rail 2 onthe stock rail 1. Thus, a jerk-free and continuous takeover of therolling stock by the tongue rail 2 will be ensured.

FIG. 5 is a cross sectional view through the stock rail head at point 4,at which the width of the stock rail 1 is most strongly reduced. Brokenline 6 indicates the standard profile of the stock rail 1, as it isformed beyond the region of abutment of the tongue rail 2. The insideedge of the standard profile indicated by broken line 6 in this caseextends at the point referenced by 7, a chamfer or undercut as formedaccording to known or prior art configurations and extending from theinside edge 7 obliquely downwards to facilitate the abutment of thetongue rail 2 being indicated by 8. By contrast, the undercut accordingto the invention is designed to increase from the region of the tip 3 ofthe tongue as far as to point 4 such that point 4 will have the stockrail head profile illustrated in FIG. 5 in full lines. The width of thestock rail 1 is, thus, reduced by the distance a with the tongue rail 2naturally being reinforced by the same extent. The curved region locatedin the transition region from the chamfer to the standard profile inthis case may be designed with a radius r1 which is smaller than theradius r2 corresponding to the curvature of the standard profile. Henceresults a displacement of the inside edge by a distance of merely b,which distance is smaller than the distance a by which the width of thestock rail is reduced.

FIG. 6, in addition to the stock rail 1, depicts the adjacent tongue 2,the carrying wheel 9 with its flange 10 being indicated by broken lines.The geometry in this case has been optimized in a manner that the innerflank 11 of the wheel flange 10 forms a tangent common to the stock rail1 and the tongue rail 2.

Overall, the invention provides a switch that offers an enhanced wearresistance and extended lay-days and, thus, provides an increased safetyby a reduced risk of fracture. The contact geometry has been optimizedso as to ensure as little influence as possible on the inside edge.

1. A switch comprising a main track and a branch track, wherein one railof each track is each configured as a tongue rail and as movable intoabutment on a respective stock rail, wherein at least one stock rail(1), in its region of abutment on the tongue rail (2), is designed tohave a reduced rail head width as compared to a region located outsidesaid region of abutment, wherein the rail head width, starting from atip (3) of a tongue of said tongue rail (2), decreases as far as to apoint (4) at which a carrying wheel comes into lateral contact with thetongue rail (2) and increases in a region following thereupon, and thetongue rail (2) is designed to be reinforced in cross section towardsthe stock rail (1) according to the reduction in the width of the stockrail head.
 2. A switch according to claim 1, wherein the width of thestock rail head is measured at a vertical distance of 10 to 20 mm from atop edge of the stock rail head.
 3. A switch according to claim 1,wherein the stock rail (1) is designed to be chamfered in the region ofabutment on the tongue rail (2) with the chamfer extending in aninclined manner from an inside edge towards a rail web.
 4. A switchaccording to claim 3, wherein an edge resulting from intersection of thechamfer with a profile of the stock rail head is designed to be rounded.5. A switch according to claim 3, wherein a profile of the stock railhead is designed with a curved region on a transition from a top edge ofthe stock rail head to the chamfer, the radius of which curved region issmaller than that of the a corresponding curved region of a standardrail profile.
 6. A switch according to claim 1, wherein a point withlargest reinforcement of the tongue rail (2), or smallest width of thestock rail head, is located at a distance from the tip (3) of thetongue, which amounts to ⅕ to ⅓, of the length of said region ofabutment of the tongue rail (2) on the stock rail (1).
 7. A switchaccording to claim 1, wherein maximum head width reduction of the stockrail (1), or maximum reinforcement of the tongue rail (2), is 2 to 5 mm.8. A switch according to claim 1, wherein vertical height of the tonguerail (2) increases in the region of abutment on the stock rail (1) inthe direction towards the end of abutment, departing from the tip (3) ofthe tongue.
 9. A switch according to claim 1, wherein an inner flank ofa flange of the carrying wheel, which encloses an angle of 50° to 70°with an axle of the carrying wheel, extends parallel with a tangentdrawn at the tongue rail (2) and the stock rail (1), or contacts therails along that tangent, at least in a region of largest reinforcementof the tongue rail (2).
 10. A switch according to claim 1, wherein theswitch is comprised of an inside curve switch, and a curve outer tonguerail is designed to be reinforced in cross section.
 11. A switchaccording to claim 2, wherein the stock rail (1) is designed to bechamfered in the region of abutment on the tongue rail (2) with thechamfer extending in an inclined manner from an inside edge towards arail web.
 12. A switch according to claim 4, wherein a profile of thestock rail head is designed with a curved region on a transition from atop edge of the stock rail head to the chamfer, the radius of whichcurved region is smaller than that of a corresponding curved region of astandard rail profile.
 13. A switch according to claim 2, wherein apoint with largest reinforcement of the tongue rail (2), or smallestwidth of the stock rail head, is located at a distance from the tip (3)of the tongue, which amounts to ⅕ to ⅓ of the length of said region ofabutment of the tongue rail (2) on the stock rail (1).
 14. A switchaccording to claim 3, wherein a point with largest reinforcement of thetongue rail (2), or smallest width of the stock rail head, is located ata distance from the tip (3) of the tongue, which amounts to ⅕ to ⅓ ofthe length of said region of abutment of the tongue rail (2) on thestock rail (1).
 15. A switch according to claim 2, wherein maximum headwidth reduction of the stock rail (1), or maximum reinforcement of thetongue rail (2), is 2 to 5 mm.
 16. A switch according to claim 3,wherein maximum head width reduction of the stock rail (1), or maximumreinforcement of the tongue rail (2), is 2 to 5 mm.
 17. A switchaccording to claim 2, wherein vertical height of the tongue rail (2)increases in the region of abutment on the stock rail (1) in thedirection towards the end of abutment, departing from the tip (3) of thetongue.
 18. A switch according to claim 3, wherein vertical height ofthe tongue rail (2) increases in the region of abutment on the stockrail (1) in the direction towards the end of abutment, departing fromthe tip (3) of the tongue.
 19. A switch according to claim 2, wherein aninner flank of a flange of the carrying wheel, which encloses an angleof 50° to 70° with an axle of the carrying wheel, extends parallel witha tangent drawn at the tongue rail (2) and the stock rail (1), orcontacts the rails along that tangent, at least in a region of largestreinforcement of the tongue rail (2).
 20. A switch according to claim 2,wherein the switch is comprised of an inside curve switch, and a curveouter tongue rail is designed to be reinforced in cross section.